dmmlib/src/bitmap/bitmap_free.c

/*
 *   Copyright 2012 Institute of Communication and Computer Systems (ICCS) 
 *
 *   Licensed under the Apache License, Version 2.0 (the "License");
 *   you may not use this file except in compliance with the License.
 *   You may obtain a copy of the License at
 *
 *       http://www.apache.org/licenses/LICENSE-2.0
 *
 *   Unless required by applicable law or agreed to in writing, software
 *   distributed under the License is distributed on an "AS IS" BASIS,
 *   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *   See the License for the specific language governing permissions and
 *   limitations under the License.
 *
 */

/**
 * @file   bitmap_free.c
 * @author Ilias Pliotas, Ioannis Koutras
 * @date   September 2012
 * @brief  free() implementation for bitmap-organized raw blocks
 */

#include "bitmap/bitmap.h"
#include "bitmap/bitmap_rb.h"
#include "bitmap/bitmap_other.h"

#include "trace.h"

#ifdef HAVE_LOCKS
#include <pthread.h>
#endif /* HAVE_LOCKS */

/** Frees the memory block inside of a specific bitmap-organized raw block.
 * @param raw_block The pointer of the raw block.
 * @param ptr       The pointer of the memory block to be freed.
 */
void bitmap_free(raw_block_header_t *raw_block, void *ptr) {
    bitmap_rb_t *rb_header;
    chunk_header_t *chunk_header;
    size_t cells_used, cell_no, bmap_index, start_pos;
    BMAP_EL_TYPE mask1, mask2;

    rb_header = (bitmap_rb_t *)((char *)raw_block + sizeof(raw_block_header_t));
    chunk_header = (chunk_header_t *)((char *)ptr - sizeof(chunk_header_t));

#ifdef HAVE_LOCKS
    pthread_mutex_lock(&raw_block->mutex);
#endif /* HAVE_LOCKS */

    cells_used = chunk_header->num_of_cells;

#ifndef REQUEST_SIZE_INFO
    TRACE_1("dmmlib - free - free'ing %zu bytes from bitmap raw block %p\n",
            cells_used * rb_header->bytes_per_cell, (void *)raw_block);
#else /* REQUEST_SIZE_INFO */
    TRACE_1("dmmlib - free - free'ing %zu bytes from bitmap raw block %p, out of "
            "which %zu were used by the application\n",
            cells_used * rb_header->bytes_per_cell,
            (void *)raw_block,
            chunk_header->requested_size);
#endif /* REQUEST_SIZE_INFO */

    cell_no = ((char *)chunk_header - ((char *)rb_header + sizeof(bitmap_rb_t)))
        / rb_header->bytes_per_cell;

    bmap_index = cell_no / BMAP_EL_SIZE_BITS;
    start_pos = cell_no % BMAP_EL_SIZE_BITS;

    // If the sum of the starting position and the cells that are used is more
    // than the available bits of one bitmap array element, then we have to
    // modify the next element as well.
    if(start_pos + cells_used <= BMAP_EL_SIZE_BITS) {
        mask1 = make_bit_mask(start_pos + 1, cells_used);
    } else {
        mask1 = make_bit_mask(start_pos + 1, BMAP_EL_SIZE_BITS - start_pos);
        mask2 = make_bit_mask((size_t) 1,
                start_pos + cells_used - BMAP_EL_SIZE_BITS);

        rb_header->bmap_array[bmap_index + 1] |= mask2;
    }
    rb_header->bmap_array[bmap_index] |= mask1;

#ifdef HAVE_LOCKS
    pthread_mutex_unlock(&raw_block->mutex);
#endif /* HAVE_LOCKS */
}